1. Field of the Invention
This invention relates to a method of electrolytic texturing whereby an electrolytic liquid is used for the texturing, say, of the surface of a magnetic hard disk substrate. The invention also relates to an electronic liquid slurry which may be used in such a texturing method.
2. Description of the Related Art
The recent trend has been to increase the memory capacity of magnetic hard disks, and there has been an increased demand to store data at higher densities. As a result, it has become necessary to reduce and stabilize the floating distance of a magnetic head from a magnetic hard disk to less than about 0.15 .mu.m and the texturing on the surface of the magnetic hard disk is required to be carried out more finely and uniformly than before without forming any abnormal protrusions on the textured surface.
In response to the recent increase in the demand for magnetic hard disks, furthermore, there has also been an increased demand for reducing the time required for the surface texturing of the magnetic hard disk substrates so as to increase their throughput. It is also being desired to increase the stock removal, that is, the amount of the material scraped off the textured surface of the magnetic hard disk substrate.
In order to reduce the abnormal protrusions which may be found formed on a magnetic hard disk surface after a texturing process, electrolytic texturing processes whereby the surface of a magnetic hard disk substrate is electrolytically treated with an electrolytic liquid and the abnormal protrusions formed thereon are removed by etching are currently being considered. In an electrolytic texturing process, an electrolytic liquid is mixed with a liquid slurry serving as free abrading particles to obtain an electrolytic liquid slurry, and the surface texturing of a magnetic hard disk substrate is carried out while the electrolytic liquid slurry thus obtained is supplied onto the surface and the aforementioned electrolytic treatment is carried out thereon. In order to increase the electrical conductivity of the electrolytic liquid, however, use is made of a liquid with a very high acidity. As a result, there arises the problem that the surface of the magnetic hard disk surface tends to be etched excessively. Another problem that arises if the electrolytic liquid is strongly acid is that the mixture of the electrolytic liquid and the liquid slurry serving as free abrading particles tends to become separated and hence that it is difficult to produce a stable electrolytic liquid slurry. Still another problem is that a strongly acid electrolytic liquid tends to corrode the apparatus for the texturing process.